1. Field of the Invention
The present invention relates to an oil pump pressure control device that facilitates a reduction in friction while maintaining characteristics identical to the pressure characteristics of a common oil pump based on the provision of a plurality of discharge sources and a newly devised method of switching oil passages.
2. Description of the Related Art
While a variable flow rate oil pump of the conventional art comprises two discharge ports configured from a single discharge port partitioned into two, because of the single rotor assembly thereof, from the viewpoint of the discharge source there is still a single discharge port. In addition, at times of high revolution when the amount of power consumed by the pump is high, oil passages of a main pump (first pump) and a sub-pump (second pump) are in communication. Accordingly, the pressure of the main pump is substantially equivalent to the pressure of the sub-pump. Although reference is made herein to a main pump and a sub-pump, obviously these pumps constitute a single pump (a single rotor), and little or no reduction in superfluous work, should it occur, can be achieved using a single pump. Furthermore, because the discharge passage of the sub-pump terminates within a valve, there is a limit to the flow rate regulation afforded by the valve alone.